Precautions for using customized experimental rotary tube furnace

Customized experimental rotary tube furnaces are commonly used in precision experiments such as material synthesis and heat treatment due to their special functions of high temperature, rotation, vacuum or atmosphere control. To ensure the safe operation of the equipment and extend its service life, the following precautions must be strictly followed during use:

1. Installation and commissioning phase
Environmental Requirements
Ventilation: The equipment should be placed in a well ventilated laboratory, away from flammable and explosive materials, and avoid the accumulation of high-temperature gases or harmful substances.
Level: Use a spirit level to adjust the furnace body, ensuring that the rotation axis is parallel to the ground to prevent eccentric wear of the furnace tube during rotation.
Power supply: Match the power cord according to the device power (such as 380V three-phase power requires ≥ 6mm ² copper wire), and install a leakage protection switch.
Bake before first use
Purpose: To remove adsorbed moisture and volatile substances in the furnace and prevent cracking at high temperatures.
Program:
In an empty furnace state, heat up to 120 ℃ at a rate of ≤ 5 ℃/min and hold for 2 hours;
Continue to heat up to 300 ℃ and hold for 3 hours;
Cool naturally to room temperature before use.
Inspection of gas path and vacuum system
Airtightness: For vacuum furnaces, use a helium mass spectrometer leak detector to detect connections such as flanges and valves to ensure leakage rate.
Gas purity: When introducing protective gases (such as N ₂, Ar), the purity should be ≥ 99.999% to avoid impurity contamination of the sample or corrosion of the furnace.

2. Operation process specification
Heating and cooling control
Speed limit:
Heating up: ≤ 10 ℃/min (slower in high temperature sections, such as ≤ 5 ℃/min above 1000 ℃);
Cooling: During forced air cooling, the fan should be turned off only when the furnace temperature drops below 200 ℃. For natural cooling, the furnace door should be kept slightly open.
Segmented insulation: Set up a middle insulation section according to the characteristics of the material (such as aluminum hydroxide, which needs to be insulated at 300 ℃ for 2 hours to remove crystal water).
Sample placement requirements
Loading capacity: The sample volume should not exceed one-third of the furnace tube volume, with a thickness of ≤ 50mm, to avoid hindering rotation or causing uneven temperature.
Location: The sample should be placed in the central area of the furnace tube, and the thermocouple temperature measurement point should be inserted into the interior of the sample or closely attached to the surface of the sample.
Fixed: Use an alumina crucible or quartz boat to carry the sample, avoiding direct contact with the inner wall of the furnace tube (to prevent adhesion or contamination).
Rotation parameter settings
Rotation speed: Adjust according to the fluidity of the material (such as powder sample rotation speed ≤ 5rpm, block sample rotation speed ≤ 2rpm);
Direction: Forward and backward alternate operation (such as switching direction every 30 minutes) to prevent material accumulation.
atmosphere control
Ventilation timing: Before heating up, introduce protective gas (flow rate ≥ 2L/min) to exhaust the air in the furnace and avoid oxidation;
Pressure monitoring: Vacuum type furnaces require real-time monitoring of vacuum degree (such as ≤ 10 Pa), while pressure type furnaces require stable control of intake pressure (such as 0.1-0.5 MPa);
Exhaust gas treatment: For toxic or corrosive gases (such as Cl ₂, H ₂ S), exhaust gas absorption devices need to be connected.

3. Safety protection measures
personal protection
Wear high-temperature gloves, protective face shields, and lab coats during operation to avoid contact with high-temperature furnace bodies or sputtered materials;
Do not wear metal jewelry (such as watches, rings) to prevent conductivity or burns.
Emergency shutdown
Press the emergency stop button immediately in the following situations:
Furnace temperature exceeding the set value by ± 10 ℃;
Furnace tube rupture or material leakage;
The rotating mechanism is stuck or makes abnormal noises;
Gas leakage or sudden drop in vacuum degree.
Fire and explosion prevention
Flammable and explosive substances (such as sulfur powder and metallic sodium) are prohibited from being placed in the furnace;
After the experiment, continue to supply protective gas until the furnace temperature drops below 100 ℃ to prevent oxygen from entering and causing oxidation or explosion.

4. Maintenance and upkeep
Daily cleaning
Clean the residue inside the furnace after each experiment (use a soft bristled brush or vacuum cleaner to avoid scratching the inner wall);
Clean the outer wall of the furnace tube (wipe with alcohol swab, do not use corrosive solvents).
regular maintenance
Weekly: Check the lubrication condition of the rotating bearings and add high-temperature lubricating grease (such as molybdenum disulfide);
Monthly: Check the resistance value of heating elements (such as silicon carbide rods with room temperature resistance of about 1-10 Ω), and replace them if the deviation exceeds ± 20%;
Every six months: replace the sealing ring (such as fluororubber O-ring), check the oil level of the vacuum pump, and replace the deteriorated oil.
Long term discontinuation
Place desiccants (such as silica gel) in the furnace and keep the furnace door slightly open to prevent moisture;
Cut off the power and gas supply, and hang a “stop using” sign.

5. Taboo behavior
Prohibit direct high-temperature heating in cold furnaces: gradually increase the temperature according to the baking program after the first use or long-term shutdown;
Prohibit overload operation: parameters such as sample size, temperature, and speed must not exceed the rated value of the equipment;
Prohibition of unmonitored operations: During the experiment, temperature, pressure, and other parameters should be regularly checked to avoid any abnormalities not being detected in a timely manner;
Unauthorized modification is prohibited: If you need to modify the air circuit, electrical circuit, or control program, please contact the manufacturer’s technical personnel.